Temperature control device

ABSTRACT

The controller  70  of the brine supply device  10  performs the PID calculation of the manipulated variable MV of the valve  14,  calculates the compensated manipulated variable MV′ by compensating the manipulated value MV, and controls the operation of the valve  14  based on the compensated manipulated variable MV′. The variation ΔMV of the manipulated variable MV becomes proportional to the variation ΔPV of the brine supply temperature Pt 1  as the operation of the valve  14  is controlled with the compensated manipulated variable MV′. This makes it possible to control temperature with a high accuracy using only one set of PID constants.

[0001] This application is based on Japanese Patent Application Nos.2000-133616, 2000-332716 and 2001-93174 filed on May 2, 2000, Oct. 31,2000 and Mar. 28, 2001, the contents of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates to a temperature control apparatus thatadjusts the temperature of a heating medium supplied to a load or thetemperature of the load itself.

[0004] 2. Description of the Related Art

[0005] For processes of manufacturing liquid crystal panels orsemiconductors, it is an essential requirement to be able to controltemperatures, so that various temperature control devices are used. Someof those temperature control devices use brine supply devices. This kindof brine supply devices supply a temperature controlled heating medium,i.e., brine, to a load circuit, where the works, such as LCD panels, aredisposed as a load, in order to maintain the temperature of the worksconstant.

[0006] For example, the Publication of Unexamined Japanese PatentApplication No. JP-A-11-183005 disclosed a brine supply deviceconsisting of a primary circuit that adjusts the brine temperature to aspecified temperature, a secondary circuit that adjusts the brinetemperature supplied to the works to a target temperature, and a valvethat adjusts the flow rate of the brine that flows in from the primarycircuit to be mixed with the flow of the secondary circuit. In thisdevice, the valve opens when the work temperature rises above the presettemperature and causes the cooler brine from the prime circuit to bemixed at a predetermined flow rate with the secondary circuit brine.This lowers the temperature of the brine being supplied to the works tothe preset temperature.

[0007] The PID control and the cascade control that combines two PIDcontrols are the two most widely used control methods for controllingthe above-mentioned valve in order to achieve the temperature control.In order to achieve a good control result by the PID control, it isnecessary to tune P (proportional band), I (integral time), and D(differential time) constants to their optimum values. The PID constantsare determined by means of a trial-and-error method while making a trialrun of the device.

[0008] In the control of the valve operation, the variation ΔMV of themanipulated variable MV obtained by PID calculations and the variationΔPV of the temperature are not proportional to each other. Therefore, agood control result is not obtainable by applying only one set of thePID constants within the temperature range to be controlled. Therefore,the temperature range to be controlled is divided into multiple segmentsand PID constants are determined for each temperature range segment. Theproblem here is that the tuning process becomes more complex andrequires a longer time to complete as multiple sets of PID constantshave to be determined.

[0009] In a process such as the one found in a semiconductormanufacturing system, a large heat load can be supplied to the workwithin a short time interval from an external heat source provided onsaid process side, or abruptly taken away. It is a system's requirementto maintain the work temperature at the predetermined temperature at alltimes despite these heat load variations from the external heat source.

[0010] In case of feedback control systems such as the PID controlsystem, the work temperature change according to the heat quantityvariation is small if the change of heat load applied to the work issmall, so that the work temperature can be maintained at thepredetermined temperature with a sufficient accuracy.

[0011] However, in a feedback control system it is impossible to makethe brine supply temperature change quick enough to follow the worktemperature change if a large heat load change is made within a shortperiod of time, which causes a hunting and instability of the controlsystem in adjusting the work temperature to the predeterminedtemperature.

SUMMARY OF THE INVENTION

[0012] The present invention was made under the circumstances describedabove and its objective is to provide a temperature control device thatcan accurately control temperatures using only one set of PID constants.

[0013] The other objective is to offer a work temperature control devicewith an improved stability in adjusting the load to a predeterminedtemperature minimizing the probability of causing load temperaturehunting phenomena.

[0014] The abovementioned object of this invention can be achieved withthe following means.

[0015] The present invention is a temperature control devicecharacterized by comprising:

[0016] a primary circuit for adjusting the temperature of a firstheating medium to a predetermined temperature;

[0017] a secondary circuit for adjusting the temperature of a secondheating medium, which is to be supplied to a load, to a targettemperature (SV(S));

[0018] a valve for adjusting the flow rate of the first heating medium,which is to be mixed with the second heating medium or conducts a heatexchange with the second heating medium;

[0019] a supply temperature detection unit for detecting the currentsupply temperature (Pt1) of the second heating medium;

[0020] a PID arithmetic unit for calculating the manipulated variable(MV) of said valve based on the target temperature (SV(S)) of the secondheating medium, the current supply temperature (Pt1) of the secondheating medium, and a predetermined set of PID constants;

[0021] a compensating arithmetic unit for calculating a compensatedmanipulated variable (MV′) by compensating the manipulated variable (MV)calculated by said PID arithmetic unit; and

[0022] a control unit for controlling the operation of said valve basedon the compensated manipulated variable (MV′); wherein

[0023] the variation (ΔMV) of the manipulated variable (MV) is madeproportional to the variation (ΔPV) of the current supply temperature(Pt1) of the second heating medium by means of controlling the operationof said valve based on the compensated manipulated variable (MV′).

[0024] The compensating factor k (0≦k≦1), by which the manipulatedvariable (MV) is multiplied at the compensation arithmetic unit, isdefined as follows:

k=1−(Pt1−PV1)(1−n)/(PV2−PV1)

[0025] where,

[0026] PV1: lower limit of the operating temperature of the secondheating medium;

[0027] PV2: upper limit of the operating temperature of the secondheating medium;

[0028] Pt1: current supply temperature of the second heating medium; and

[0029] n: a constant for limiting the manipulated variable when thesecond heating medium supply temperature is equal to the upper limitPV2.

[0030] According to the temperature control unit described above, thesupply temperature of the second heating medium can be adjusted to adesired temperature by means of only one set of PID constants for a widetemperature range from the lower limit to the upper limit of theoperating temperature of the second heating medium. Consequently, itbecomes possible to adjust the load to a predetermined temperature bymeans of only one set of PID constants. Since it is required todetermine only one set of PID constants, the determination process canbe easily performed and the user can easily change the setup temperatureof the load.

[0031] The present invention is a temperature control device thatmaintains the temperature of the load to a setup temperature (SV(R)),while the heat load added thereto by an external heat source is changed,comprising:

[0032] a supply temperature detection unit for detecting the currentsupply temperature (Pt1) of a heating medium supplied to the load;

[0033] a load temperature detection unit for detecting the currenttemperature (Pt2) of the load;

[0034] an adjusting unit for adjusting the supply temperature (Pt1) ofthe heating medium;

[0035] an acquiring unit for acquiring in advance a first temperaturechange curve (L1) of the load when said heat load is changed whilemaintaining the supply temperature (Pt1) of the heating medium constant;

[0036] a first calculating unit for calculating an imaginary secondtemperature change curve (L2) of a load (W), which is in axial symmetrywith said first temperature change curve (L1), based on the setuptemperature (SV(R)) of the load;

[0037] a second calculating unit for calculating a target temperaturechange curve (L3) of the heating medium for realizing said secondtemperature change curve (L2); and

[0038] a control unit for controlling said adjusting unit so that thesupply temperature (Pt1) of the heating medium changes according to saidtarget temperature change curve (L3) when the heat load applied to theload by said external heat source is changed.

[0039] According to the temperature control unit described above, sincethe supply temperature of the heating medium is adjusted predictivelybefore a temperature change occurs in the load due to the heat loadchange, the difference between the load temperature and the setuptemperature does not grow as large as in feedback controls such as thePID control. Consequently, the load temperature can be maintainedconstant with a smaller hunting compared to the feedback control evenwhen a large heat load change occurs in a short period of time, thusmaking it possible to achieve a higher control stability in adjustingthe load to a setup temperature.

[0040] Other objects, features and characteristics of the invention willbecome apparent with reference to following descriptions and preferredembodiments exemplified in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0041]FIG. 1 is the first embodiment of the brine supply device to whichthe temperature control device of the invention is applied;

[0042]FIG. 2 is a block diagram showing a controller that controls theoperation of the brine supply device;

[0043]FIG. 3 is a graph showing a compensating factor k (0≦k≦1) that ismultiplied to the manipulated variable MV of a solenoid valve and thebrine supply temperature Pt1;

[0044]FIG. 4 and FIG. 5 constitute a flow chart describing the operationof the first embodiment;

[0045]FIG. 6 is a chart conceptually showing an example of temperaturechange in the first embodiment;

[0046]FIG. 7 is a constitutional diagram showing a variation fordetecting the current temperature of the load by measuring thetemperature of the brine returning from the load;

[0047]FIG. 8 is a constitutional drawing showing the second embodimentof the brine supply device to which the temperature control device ofthe invention is applied;

[0048]FIG. 9 is a block diagram showing a controller that controls theoperation of the brine supply device;

[0049]FIG. 10 is a descriptive drawing of the basic operating principle;

[0050]FIG. 11 through FIG. 16 constitute a flowchart describing theoperation of the second embodiment;

[0051]FIG. 17 is a chart conceptually showing an example of the worktemperature and a brine supply temperature changes in the sampling mode;

[0052]FIG. 18A is a chart conceptually showing an example of the worktemperature when the heat load to the work from the external heat sourceis changed while maintaining the temperature of the brine supplied tothe work constant; and

[0053]FIG. 18B is a chart conceptually showing an example of the worktemperature and the brine supply temperature changes in the worktemperature control mode.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0054] The temperature control device according to the present inventionwill be described in detail according to preferred embodiments shown inthe accompanying drawings.

Embodiment 1

[0055] The first embodiment of the brine supply device as a temperaturecontrol device will be described below referring to FIG. 1.

[0056] The brine supply device 10 is connected to a load circuit 20where a work W is disposed as a load. The brine supply device 10includes: a primary circuit 11 for adjusting the temperature of brine(first heating medium); a secondary circuit 12 for adjusting the brine(second heating medium) supplied to the work W to a target temperature;a connecting line 13 to connect the primary circuit 11 and the secondarycircuit 12, and a valve 14 provided in a connecting line 13. Brine of arelatively low temperature circulates in the primary circuit 11 andbrine of a relatively high temperature circulates in the secondarycircuit 12. A portion of the brine in the primary circuit 11 mixes withthe brine in the secondary circuit 12 through the connecting line 13.The flow rate of the brine from the primary circuit 11 to be mixed withthe brine in the secondary circuit 12 is adjusted by the opening/closingoperations of the valve 14 to control the supply temperature of thebrine to be supplied to the work W. The temperature of the work W isadjusted by the temperature controlled brine. The controller 70 controlsthe operation of the brine supply device 10. The brine to be used herecan be, e.g., fluorine based brine, cold water, pure water, refrigerant,etc., and a brine suitable for the work W will be selected.

[0057] More specifically, the primary circuit 11 includes a brine tank41 for storing the brine, a first pump 42 for circulating the brine, aheat exchanger 43, and a valve 44. These circuit elements are connectedby means of pipes 45 a through 45 d. The brine tank 41 is sealed with acap so that it is not communicating with the atmosphere, but it is not apressure vessel to be controlled by the regulation, i.e., it isconstructed as a semi-sealed vessel. Since the purpose of the first pump42 is to circulate the brine through the primary circuit 11, itsdisposition does not necessarily have to be between the brine tank 41and the heat exchanger 43. For example, it can be provided in line withthe pipe 45 c on the outlet side of the heat exchanger 43. The brine iscooled by exchanging heat with a coolant supplied to the heat exchanger43. A fourth temperature sensor 84 to detect the cooled brine'stemperature Pt4 is provide on the pipe 45 c on the outlet side of theheat exchanger 43. The setup temperature of the work W in the firstembodiment is relatively low (for example, 40° C. through 60° C.) and arefrigerant is used as a coolant. The coolant is cooled by arefrigerator 50.

[0058] The refrigeration cycle of the refrigerator 50 includes acompressor 51 for compressing the refrigerant, a condenser 52, throughwhich cooling water runs, an expansion valve 53, and a heat exchanger 43that serves as an evaporator. The brine temperature Pt4 is adjusted byadjusting the temperature of the refrigerant that flows into the heatexchanger 43. The temperature of the refrigerant is controlled bycontrolling the refrigerating capacity of the refrigerator 50. Thecapacity control for the refrigerator 50 is conducted by controlling thehot gas flow rate. The refrigerator 50 has a hot gas bypass pipe 54 thatconnects the outlet side of the compressor 51 and the outlet side of theexpansion valve 53, a capacity regulating valve 55 and a first solenoidvalve 56 provided in line with a hot gas bypass pipe 54, and a secondsolenoid valve 57 provided in line with a pipe extending from the outletof the condenser 52 to the expansion valve 53. Each of the first and thesecond solenoid valves 56 and 57 is open when the other is closed andclosed when the other is open. When the first solenoid valve 56 isopened, the relatively high temperature gaseous refrigerant compressedby the compressor 51 will pass through the capacity regulating valve 55and the hot gas bypass pipe 54, and will mix with the refrigerant thatis relatively cooled due to adiabatic expansion by the expansion valve53. The flow rate of the hot gas flowing toward the output side of theexpansion valve 53 will be determined by the setup value of the capacityregulating valve 55 and the opening time of the first solenoid valve 56.As a result of the opening/closing actions of the first and secondsolenoid valves 56 and 57, the temperature of the refrigerant that flowsinto the heat exchanger 43 will be adjusted and the brine cooled by theheat exchanger 43 will be adjusted to a predetermined temperature as aresult. The controller 70 controls the first and the second solenoidvalves 56 and 57 in order to make the brine temperature Pt4 will belower than the brine target temperature SV(S) that is supplied to thework W by a predetermined temperature (e.g., 8° C.).

[0059] The coolant that cools the brine can be arbitrarily selectedaccording to the setup temperature of the work W. For example, if thesetup temperature of the work W is relatively higher, cold water can beused as the coolant.

[0060] The secondary circuit 12 includes an electric heater (correspondsto a heating unit) 61 that heats the brine, a second pump 62 forcirculating the brine, a supply port 63 that supplies the brine to theload circuit 20, and a return port 64, through which the brine which haspassed the load circuit 20. These circuit elements are connected bymeans of pipes 65 a through 65 d. The secondary circuit 12 is connectedto the brine tank 41 via a pipe 65 e that branches off from the pipe 65d. Brine of an amount equivalent to the amount mixed into the secondarycircuit 12 from the primary circuit 11 through the valve 14 is returnedto the brine tank 41 through the piping 65 e. Brine will be heated bythe electric heater 61 and the temperature of the work W can be quicklyraised to a desired temperature. The heating unit used here is notlimited to the electric heater 61 but can be any device as long as ithas a capability to heat brine. Also, since the primary purpose of thesecond pump 62 is to circulate brine in the secondary circuit 12, itslocation is not limited only to the position for sending out the brineheated by the heater 61 as indicated in the drawing. For example, it canbe located on the pipe 65 a at the entrance side of the heater 61. Thisbrine supply device 10 is formed in such a way that it does not changethe brine flow rate while it is being operated. Therefore, a pumpcapable of discharging brine at a fixed flow rate is used as the secondpump 62. However, a pump with a selectable brine flow rate setting canbe used to meet various specifications required for the brine supplydevice 10.

[0061] The connecting line 13 is provided between the pipe 45 c and thepipe 65 a. The valve 14 provided in the connecting line 13 is a solenoidvalve that turns on and off the communication between the primarycircuit 11 and the secondary circuit 12. In order to lower the brinetemperature that supplied brine to the work W, the valve 14 opens toallow a portion of the brine that circulates through the primary circuit11 to be introduced to the inlet side of the heater 61 through theconnecting line 13.

[0062] In the format that introduces a portion of the brine in theprimary circuit 11 to the secondary circuit 12 as needed, it is notnecessary to cool the entire amount of brine existing in the brinesupply device 10 and the brine in the secondary circuit 12 will becooled no more than necessary. As a result, the energy loss in reheatingby the heater 61 can be held to a minimum thus contributing to a moreefficient operation of the brine supply device 10. As the brinetemperature Pt4 of the primary circuit 11 is adjusted lower than thebrine target temperature SV(S), it is possible to lower the temperatureof the work W quickly by lowering the brine supply temperature Pt1 evenwhen the temperature increase of the work W is large.

[0063] The load circuit 20 is typically built into a manufacturingdevice, an inspection device or an isothermal device. For example, theload circuit 20 is built into a film forming device 30, which is used toform thin films on glass substrates used for LCD panels. In this case,the glass substrate is the work W.

[0064] The load circuit 20 includes an input pipe 21 that connects tothe supply port 63, a chamber 22 that contains the work W, and an outletpipe 23 that connects to the return port 64. The work W is mounted onthe plate 24. The plate 24 is heated/cooled by the brine supplied to thechamber 22 to adjust the work temperature to the setup temperature.

[0065] The load circuit 20 is further provided with an external heatsource 31 on the process side that adds a heat load to the work W. Theexternal heat source 31 consists of an electric heater 32, to which aspecified current of a specified voltage is applied from the powersource 33. Joule Heat generated by the electric heater 32 is applied tothe work W to raise the temperature. “The external heat source 31” isthe general name given to various devices that heat the work W and doesnot mean only an electric heater.

[0066] The pipe 65 c is provided with a first temperature sensor 81 todetect the current supply temperature Pt1 of the brine being supplied tothe load W. The load circuit 20 is provided with a second temperaturesensor 82 to detect the current temperature Pt2 of the work W. The firsttemperature sensor 81 corresponds to the supply temperature detectionunit and the second temperature sensor 82 corresponds to the loadtemperature detection unit. The temperature sensors 81, 82 and 84consist of resistance thermometers, thermocouples, etc. Since thetemperature of the plate 24 is approximately equal to the worktemperature Pt2, the work temperature Pt2 is indirectly measured bymeasuring the plate temperature in the case shown in the figure.

[0067] The constitution of the controller 70 that controls the operationof the brine supply device 10 will be described below in reference toFIG. 2.

[0068] The sensors 81, 82, and 84 are connected to a CPU 71, i.e., thecontrol unit, to feed the detection signals of the brine supplytemperature Pt1, the work temperature Pt2, and the brine temperature Pt4of the primary circuit 11. The CPU 71 is further connected with a setupunit 72, a target temperature arithmetic unit 73, a PID arithmetic unit74, a compensation arithmetic unit 75, a ROM 76, a RAM 77 and a timer78. The setup unit 72 consists of an input device such as a digitalkeypad and is used for setting up the setup temperature SV(R) of thework W. The target temperature arithmetic unit 73 calculates the targettemperature SV(S) of the brine to be supplied to the work W based on thework setup temperature SV(R), the work temperature Pt2, and the brinesupply temperature Pt1. The PID arithmetic unit 74 conducts a PIDcalculation of the manipulated variable MV for the valve 14 based on thebrine target temperature SV(S), the brine supply temperature Pt1, and apredetermined set of PID constants (P, I and D). The PID arithmetic unit74 also conducts a PID calculation of the manipulated variable mv forthe electric heater 61 based on the PID constants for the electricheater 61. The compensation arithmetic unit 75 calculates thecompensated manipulated variable MV′ by compensating the manipulatedvariable MV calculated by the PID arithmetic unit 74. The CPU 71 outputsthe compensated manipulated variable MV′ to the valve 14 to control theoperation of the valve 14. The CPU 71 munipulated variable mv toswitching elements including those of the SSR (solid state relay) of theelectric heater 61 to control the operation of the electric heater 61.The CPU 71 outputs control signals to the first and second solenoids 56and 57 for the capacity control of the refrigerator 50. The ROM 76stores various parameters and programs necessary for controlling theoperation of the brine supply device 10 in addition to various formulaerelated to the compensation factor to be multiplied to the manipulatedvariable MV. The RAM 77 stores the PID constants necessary for the PIDcalculation and others.

[0069] The CPU 71 is also connected with a power source 33 of theprocess side and receives the on/off signals corresponding to the powersupply from the power source 33 to the electric heater 32 and the outputvalue signal concerning the power supplied to the heater 32.

[0070] The PID constants are obtained by a simulation based on theperformance characteristics of the brine supply device 10 and thespecifications of the film forming device 30. When the brine supplydevice 10 is shipped from the plant, it will be set up with the PIDconstants as obtained in the above. However, it is impossible toaccurately simulate the entire dynamic characteristics of the brinedsupply device 10 and the film forming device 30. Thus, the final PIDconstants are determined by a trial-and-error method during the overalltest run of the brine supply device 10 and the film forming device 30.The determined PID constants are stored in the RAM 77.

[0071] The compensation factor k will be described below with referenceto FIG. 3.

[0072] As shown in the figure, the compensation factor k is inverseproportional to the brine supply temperature Pt1. The compensationfactor k is defined as follows:

k=1−(Pt1−PV1)(1−n)/(PV2−PV1)

[0073] where,

[0074] PV1: lower limit of the operating temperature of the brine;

[0075] PV2: upper limit of the operating temperature of the brine;

[0076] Pt1: current supply temperature of the brine; and

[0077] n: a constant for limiting the manipulated variable

[0078] MV when the brine supply temperature is equal to the upper limitPV2.

[0079] The lower limit PV1 is determined from the lower limittemperature of the work W, while the upper limit PV2 is determined fromthe upper limit temperature of the work W. The lower and upper limits ofthe work W are part of the specifications of the film forming device 30.The system must be able to control the work temperature within thetemperature range determined by the lower and upper limits of the workW. Therefore, the cooling capacity of the refrigerator 50 is determinedbased on the brine circulating flow rate, the lower limit temperature ofthe work W, the heat generated by the load circuit 20, etc., and theheating capability of the electric heater 61 is determined by the brinecirculating flow rate, the upper limit temperature of the work W, etc.

[0080] When the brine supply temperature Pt1 is equal to the lower limitPV1 (Pt1=PV1), the compensation factor k is set to “1,” and themanipulated variable MV of the valve 14 obtained by the PID calculationis equal to the compensated manipulated variable MV′. On the other hand,when the brine supply temperature Pt1 is equal to the upper limit PV2(Pt1=PV2), the compensation factor k is set to “n,” as k=1−(1−n). This“n” is a value to limit the opening operation time of the valve 14 whenthe brine supply temperature Pt1 is equal to the upper limit PV2.

[0081] The process of determining the “n” value will be described belowusing a numerical example. For the sake of the simplicity ofdescription, let us replace brine with water. Let us also assume thatthe lower limit PV1 is 10° C. and the upper limit PV2 is 90° C. Let usalso assume that the water temperature Pt4 of the primary circuit 11 isfixed at 0° C. and the cooling capability of the refrigerator 50 is 1500kcal/hr. Let us also assume that the heat generated by the load circuit20 is 1500 kcal/hr, and the flow rate of the water supplied to the workW by the second pump 62 is 10 liter/minute. Let us also assume that theflow rate of the water that is mixed into the secondary circuit 12through valve 14 is x liter/minute, the flow rate of the water returningto the tank 41 from the pipe 65 d through the pipe 65 e to the tank 41is x liter/minute, and the flow rate of the water returning from thepipe 65 d to the pipe 65 a is y (=10−x) liter/minute.

[0082] The temperature rise in the water that has passed the work W is:1500[kcal/hr]/(60[min/hr]×10[liter/min]×1[kcal/(liter·° C.)])=2.5[° C.].

[0083] When the operating water temperature is equal to the lower limitPV1, i.e., 10° C., the flow rate x of the 0° C. water that required tomake the water temperature to 10° C. is calculated from the relation:x[liter/min]×0[° C.]+y [liter/min]×(10+2.5)[° C.]=10[liter/min]×10[°C.], as x=2[liter/min].

[0084] The PID constants (P, I and D) for the valve 14 are determinedbased on the lower limit PV1 of the brine operating temperature. Morespecifically, the PID constants of the valve 14 are determined in such away that the manipulated variable MV of the valve 14 becomes 100% (fullyopened) when the brine operating temperature is equal to the lower limitPV1 and that the refrigerator 50 operates at the rated capacity. In theabove numerical example, the valve 14 becomes fully open as 100%manipulated variable MV is applied when the water operating temperatureis at the lower limit, i.e., 10° C. The specifications of the connectingline 13 and the valve 14 (e.g., diameter) are determined in such a waythat the water flows at a rate of 2 liter/minute.

[0085] On the other hand, if the water operating temperature is 90° C.,i.e., the upper limit PV2, the flow rate x of the 0° C. water requiredto make the water temperature to 90° C. is calculated from the relation:x[liter/min]×0[° C.]+y [liter/min]×(90+2.5)[° C.]=10[liter/min]×90[°C.], as x=0.27[liter/min].

[0086] If the manipulated variable MV of the valve 14 is calculated as0.27[liter/min]×100[%]/2[liter/min]=13.5[%], the above flow rate can berealized. More specifically, the above flow rate can be realized byusing the proportional band P of 1/0.135=7.4 times of the value of theproportional band P when the operating temperature of water is equal tothe lower limit PV1.

[0087] However, as a result of using a set of PID constants, which isdetermined when the assumption that the water operating temperature is10° C., the manipulated variable MV when the water temperature is 90° C.is not 13.5% but rather 100%. This makes it impossible to control thewater temperature to be supplied to the work W to the target temperatureof 90° C. because the flow rate of the 0° C. water is too much. As aresult, the heating by the electric heater 61 increases and waste ofenergy occurs. Moreover, since a lot of water at 92.5° C. returns to thetank 41, overloading of the compressor 51 of the refrigerator 50results.

[0088] Therefore, in order to limit the manipulated variable MV when thesupply temperature Pt1 is equal to the upper limit PV2, “n” is set to0.27[liter/min]/2[liter/min]=0.135.

[0089] Once the “n” value is set like this, the temperature followingcontrol is executed. When the supply temperature Pt1 is equal to 10° C.,i.e., the lower limit PV1 (Pt1 =PV1), the compensation factork=1−(Pt1−PV1)(1−0.135)/(PV2−PV1)=1. As a result, if the manipulatedvariable MV is calculated to be 100%, the compensated manipulatedvariable MV′ actually applied to the valve 14 is also 100[%]×k=100[%], 2liter/minute of water flows through the valve 14, and the watertemperature will be controlled to 10° C. The refrigerator 50 alsooperates at the rated capacity of 1500 kcal/hr.

[0090] When the supply temperature Pt1 is 90° C., i.e., the upper limitPV2 (Pt1=PV2), the compensation factork=1−(Pt1−PV1)(1−0.135)/(PV2−PV1)=0.135. As a result, even if themanipulated variable MV is calculated to be 100%, the compensatedmanipulated variable MV′ actually applied to the valve 14 is also100[%]×k=13.5[%], so that 0.27 liter/minute of water flows through thevalve 14, and the water temperature will be controlled to 90° C. Therefrigerator 50 does not cause overloading in this case and operates atthe rated capacity of 1500 kcal/hr.

[0091] As can be seen from the above, by controlling the valve 14 at thecompensated manipulated variable MV′ obtained by multiplying themanipulated variable MV with the compensating factor k, the variationΔMV of the manipulated variable MV becomes proportional to the variationΔPV of the supply water temperature Pt1. In other words, the supplywater temperature Pt1 can be adjusted to a desired temperature withinthe range of 10° C. through 90° C. using only one set of PID constants.Moreover, when the manipulated variable MV is 100%, the refrigerationcapacity of the refrigerator 50 is constantly 1500 kcal/hr regardless ofthe water temperature as long as it is within the range of 10° C.through 90° C. Therefore, it provides an effect of preventing theoverload of the refrigerator 50.

[0092] In the first embodiment, the controller 70 controls the operationof the valve 14 with the compensated manipulated variable MV′ obtainedby multiplying the manipulated variable MV based on the PID calculationwith the compensation factor k. This control makes the variation ΔMV ofthe manipulated variable MV proportional to the variation ΔPV of thebrine supply temperature Pt1. This means that the brine supplytemperature Pt1 can be adjusted to any desired temperature using onlyone set of PID constants within a range from the lower limit PV1 to theupper limit PV2 of the brine operating temperature.

[0093] The reason the manipulated variable mv of the electric heater 61is not compensated is that the variation Δmv of the manipulated variablemv is approximately proportional to the variation of the brinetemperature that passed the electric heater 61 regardless of thetemperatures. Of course, the operation of the electric heater 61 canalso be controlled, similar to the case of the valve 14, by thecompensated manipulated variable obtained by multiplying the manipulatedvariable mv with the compensating factor.

[0094] If the constant-value control, in which the target temperature ofbrine is constant, is applied, there will be many cases in thisembodiment where the time constant exceeds one hour depending on thework W, so that it will be impractical to use. In a system with such alarge time constant, the cascade control is normally used. The cascadecontrol is a kind of the follow-up value control where the target valuechanges with time.

[0095] The cascade control needs two adjusters, i.e., a firsttemperature adjuster that uses the work temperature as the setup value,and a second temperature adjuster that controls the brine supplytemperature. The setup value of the first temperature adjuster is fixed.The first temperature adjuster conducts a PID calculation based on thedeviation between the fixed setup value and the work temperature andoutputs the manipulated value. On the other hand, the second temperatureadjuster receives the manipulated variable outputted from the firsttemperature adjuster as the input, conducts a PID calculation on it, andoutputs the result as the manipulated variable. As can be seen from theabove, the cascade control is essentially a method based on a PIDcalculation by means of two temperature adjusters so that it cannotcontrol the brine supply temperature accurately by simply setting uponly one set of PID constants. Therefore, it is necessary to divide thebrine usage temperature range into, e.g., eight segments and determinePID constants for each temperature adjuster for each segment oftemperature range. Moreover, the PID constants of each temperatureadjuster have to be changed according to the work setup temperature.

[0096] However, the user cannot change the PID constants easily.Therefore, it is impractical to adopt the cascade control on a brinesupply device where heating and cooling are applied repeatedly on thework W and the setting temperature has to be changed substantially andfrequently. Moreover, since the final PID constants need to bedetermined by a trial-and-error method, the process of determining theconstants become more complicated and time consuming as the number ofsets of PID constants is increased to improve the accuracy of thetemperature control.

[0097] On the contrary, the brine supply device 10 of this embodimentcovers the temperature range from the lower limit PV1 to the upper limitPV2 of the operating brine temperature with only one set of PIDconstants as mentioned above. Therefore, it is a preferable control forcases in which the setting temperatures of the work W vary substantiallyand frequently. Since only one set of PID constants is required to bedetermined, the determining process can be done relatively easily andquickly.

[0098] The operation of the first embodiment will now be describedreferring to FIG. 4 and FIG. 5 that show the flow chart as well as FIG.6.

[0099] When the power to the brine supply device 10 is turned on (S11),the controller 70 becomes ready to accept the user's input of the worksetup temperature SV(R) (S12). When the work setup temperature SV(R) isset and the start switch is depressed (S13: YES), the first and secondpumps 42 and 62 start to run (S14). Brine runs through the primarycircuit 11 and secondary circuit 12 at a constant flow rate with thehelp of the pumps 42 and 62. The controller 70 also turns on a motor torun the compressor 51 and thus the refrigerator 50 (S15), and turns onthe electric heater 61 (S16).

[0100] The first temperature sensor 81 detects the brine supplytemperature Pt1 and the second temperature sensor 82 detects the worktemperature Pt2 (S17).

[0101] The controller 70 calculates the deviation between the work setuptemperature SV(R) and the work temperature Pt2, i.e., dt=SV(R)−Pt2(S18). The controller 70 determines the initial value of the brinetarget temperature SV(S) based on a formulaSV(S)=Pt1+dt=Pt1+(SV(R)−Pt2)(S19).

[0102] The controller 70 turns the first and second valves 56 and 57 onand off to control the hot gas flow in order to control the capacity ofthe refrigerator 50 (S20). The brine temperature Pt4 at the outlet ofthe heat exchanger 43 is adjusted to a temperature lower than the brinetarget temperature SV(S) by a specified margin (e.g., 8° C.).

[0103] The controller 70 conducts a PID calculation on the manipulatedvariable MV of the valve 14 based on the brine target temperature SV(S),the brine supply temperature Pt1, and one set of PID constants for thevalve 14 (S21 shown in FIG. 5). The controller 70 also conducts a PIDcalculation on the manipulated variable mv of the electric heater 61based on the PID constants for the electric heater 61 (S21).

[0104] The controller 70 calculates the compensated manipulated variableMV′ multiplying the manipulated variable MV of the valve 14 with thecompensation factor k (S22). The compensated manipulated variable MV′thus obtained is outputted to the valve 14 to control the valve 14 onand off (S23). The controller 70 does not compensate the manipulatedvariable mv of the electric heater 61. The manipulated variable mv isoutputted to the electric heater 61 to control the operation of theelectric heater 61 (S24).

[0105] Next, the controller 70 makes a judgment whether the brine supplytemperature Pt1 has reached the brine target temperature SV(S) (S25).More specifically, it makes a judgment whether the absolute value ofSV(S)−Pt1 is less than the error tolerance α. The tolerance α is, forexample, 0.1 to 0.2° C.

[0106] If it has not reached the brine target temperature (S25: NO), thecontroller 70 makes a judgment whether the brine supply device 10 isstill operating (S30). If it is still operating (S30: YES), the stepsS20 through S25 will be repeated; if it is not operating anymore (S30:NO), the process will be terminated.

[0107] When the brine supply temperature Pt1 has adjusted to the brinetarget temperature SV(S) (S25: YES), the controller 70 makes a judgmentwhether the work temperature Pt2 has reached the work setup temperatureSV(R) (S26). More specifically, it makes a judgment whether the absolutevalue of SV(R)−Pt2 is less than the error tolerance β. The tolerance βis, for example, 0.1 to 0.2° C.

[0108] If it has reached the work setup temperature (S26: YES), thecontroller 70 makes a judgment whether the brine supply device 10 isstill operating (S30) while maintaining the current brine targettemperature SV(S). If it is still operating (S30: YES), the steps S20through S26 will be repeated; if it is not operating anymore (S30: NO),the process will be terminated.

[0109] When the work temperature Pt2 has not adjusted to the work setuptemperature SV(R) (S26: NO), the controller 70 makes a judgment whetherthe work temperature Pt2 is lower than the work setup temperature SV(R)(S27).

[0110] If the work temperature Pt2 is higher than the work setuptemperature SV(R) (S27: NO), the brine target temperature SV(S) is rest0.1° C. lower (S28). On the other hand, if the work temperature Pt2 islower than the work setup temperature SV(R) (S27: YES), the brine targettemperature SV(S) is reset 0.1° C. higher. The process advances to thestep S30, and if the brine supply device 10 is still operating (S30:YES), the steps S20 through S29 will be repeated; if it is not operatingany more (S30: NO), the process will be terminated.

[0111] According to this first embodiment, the heat exchange quantitybetween brine and the work W does not change abruptly as the worktemperature is controlled by means of the temperature information alonewithout changing the brine circulation amount. Thus, it seldom causeshunting phenomena in the work temperature, consequently improving thecontrol stability in adjusting the work W to the setup temperature. Forexample, the temperature of the work W can be controlled to such a highaccuracy of ±0.5° C.

[0112] Moreover, the valve 14 is on/off controlled by means of thecompensated manipulated variable MV′ obtained by multiplying themanipulated variable MV, which is obtained by a PID calculation, withthe compensation coefficient k. As a result of this control, thevariation ΔMV of the manipulated variable MV is proportional to thevariation ΔPV of the brine supply temperature Pt1. Therefore, it ispossible to adjust the brine supply temperature Pt1 to a desiredtemperature within a broad range from the lower limit PV1 to the upperlimit PV2 of the brine operating temperature using only one set of PIDconstants. As a result, the work W can be adjusted to a desiredtemperature using only one set of PID constants. Since it requires onlyone set of PID constants, the process of determination is quite simple.Also, the user can change the setting temperature of the work W easily.

Modified Example

[0113] As the brine of the primary circuit 11 is mixed with the brine inthe secondary circuit 12 via the valve 14 in the embodiment describedabove, the first heating medium is the same substance as the secondmedium. The invention is not limited to such a case, however, and it canbe applied to a case where an adjustment is made by means of the valve14 on the flow rate of the first heating medium that exchanges heat withthe second heating medium. In such a case, a heat exchanger is providedfor exchanging heat between the first heating medium and the secondheating medium, and the first heating medium can be a differentsubstance from the second heating medium.

[0114] Although an embodiment is described above where the invention isapplied to a follow-up value control where the target temperature SV(S)of the second heating medium changes with time, the invention can beapplied to a constant-value control where the target temperature SV(S)of the second heating medium stays constant. It is possible in this casealso to adjust the supply temperature of the second heating medium to adesired temperature within a broad range from the lower limit PV1 to theupper limit PV2 of the second heating medium using only one set of PIDconstants.

[0115] While the work temperature Pt2 is detected by measuring thetemperature of the plate 24, on which the work W is mounted, by means ofthe second temperature sensor 82, the detection of the currenttemperature of the work W is not limited to such a case. As shown inFIG. 6, there is a certain correlation between the current temperatureof the work W and the temperature of the brine returning from the loadcircuit 20. Therefore, as the brine supply device 10A shown in FIG. 7,the current temperature of the work W can be indirectly determined fromthe return brine temperature Pt3 by providing a third temperature sensor83 in the return pipe 65 d and measuring the temperature Pt3 of thebrine returning from the load circuit 20. It is also possible to makethe second temperature sensor 82 contact directly with the work W anddirectly measure the current temperature of the work W. Moreover, it ispossible to determine the current temperature of the work W by measuringthe temperature of the brine that comes in contact with the work W.

[0116] Although the valve 14 was indicated as a solenoid valve, anon/off valve, to control the flow rate of the first heating medium tozero or maximum, the valve 14 can be a flow control valve that controlsthe flow rate of the first heating medium continuously.

Second Embodiment

[0117] The second embodiment of the brine supply device as a temperaturecontrol device will be described referring to FIG. 8. The members thatare identical to those used in the first embodiment are identified withthe same codes and their descriptions are partially omitted.

[0118] The brine supply device 10B includes a primary circuit 11, asecondary circuit 12, a connecting line 113 that connects a primarycircuit 11 and a secondary circuit 12, and a valve 114 provided in theconnecting line 113 as in the case of the brine supply device 10. Theoperation of the brine supply device 10B is controlled by a controller170.

[0119] The constituting elements of the secondary circuit 12 areconnected by multiple pipes 65 a through 65 d as well as 65 g and areconnected with a brine tank 41 through a pipe 65 f branching off fromthe pipe 65 d. The pipe 65 f has a valve 66 for controlling the flowrate of the brine returning to the brine tank 41.

[0120] The connecting line 113 is provided between a pipe 45 c and thepipe 65 b. A valve 114 provided in the connecting line 113 is a solenoidvalve that turns on and off the communication between the primarycircuit 11 and the secondary circuit 12. In order to lower thetemperature of the brine to be supplied to the work W, the valve 114 isopened and a portion of the bring that is circulating the primarycircuit 11, or the amount necessary for cooling, is introduced into theoutlet side of the heater 61 through the connecting line 113.

[0121] The second embodiment further includes a buffer tank 67 betweenthe valve 114 and the work W. The buffer tank 67 is placed at a locationimmediately behind the point where the relatively low temperature brinebrought from the primary circuit 11 meets with the relatively hightemperature brine from a heater 61. The buffer tank 67 has functions ofpromoting the mixing of the low temperature brine and the hightemperature brine and removing temperature uneveness from the brine tobe supplied to a load circuit 20. The capacity of the buffer tank 67 ischosen to be sufficient to provide said functions. It is also possiblenot to connect the pipe 65 b and the connecting line 113, but ratherconnect them independently to the buffer tank 67 and make the lowtemperature brine and the high temperature brine to mix inside thebuffer tank 67 to remove the temperature uneveness. It is also possibleto have buffer plates in the buffer tank 67 to promote mixing of the lowtemperature brine and the high temperature brine.

[0122] The return pipe 65 d is provided with a third temperature sensor83 to detect the return brine temperature Pt3 in the return pipe 65 d.The third temperature sensor 83 is also constituted of a resistancethermometer, etc., similar to other temperature sensors 81, 82 and 84. Aflow rate sensor 85 is also provided in the return pipe 65 d to detectthe circulating flow F of the brine. The flow rate sensor 85 consists ofa common flow meter using an orifice, and a converter that converts themeasured amount into an electrical signal to be outputted to thecontroller 170.

[0123] The constitution of the controller 170 that controls theoperation of the brine supply device 10B will be described below inreference to FIG. 9.

[0124] The sensors 81 through 85 are connected to a CPU 171 to feed thedetection signals of the brine supply temperature Pt1, the worktemperature Pt2, the brine return temperature Pt3, the brine temperaturePt4 of the primary circuit 11, and the brine circulating flow rate F.The CPU 171 outputs control signals to the refrigerator 50, the electricheater 61 and the valve 114 to control their operations. A ROM 176stores, in addition to the program for setting up the brine supplytemperature predictively, various parameters and programs to control theoperation of the brine supply device 10B. The CPU 171 also receiveson/off signals corresponding to the power supply from a power source 33to an electric heater 32 as well as the output value signal of theelectric power supplied to the electric heater 32. The CPU 171 detectsany change of the heat load applied to the work W by the electric heater32 and the heat quantity actually added to the work W. The electricheater 32 on the process side will be hereinafter called the processheater 32. The CPU 171 will function as the acquiring unit, calculatingunit and controlling unit of the invention.

[0125] The basic operating principle of the temperature control systemwill be described below referring to FIG. 10.

[0126] The temperature control device maintains the temperature of thework W to a specified work setup temperature SV(R) by the temperaturecontrolled brine while heat load applied by an external heat source 31changes.

[0127] It acquires a temperature change curve L1 of the work W inadvance when the heat load from the external heat source 31 to the workW is changed while the brine supply temperature supplied to the work Wis maintained constant.

[0128] The “change of heat load” here, as shown in FIG. 10, can beeither a change from an off-state (heat load 0%) as no heat load isapplied to the work W at time t0 to an on-state (heat load 100%) as aheat load of a specified quantity of heat is applied, or a change froman on-state (heat load 100%) as a heat load of a specified quantity ofheat is applied to the work W at time t1 to an off-state (heat load 0%)as no heat load is applied.

[0129] In the former case of heat load change, the first temperaturechange curve L1 shows a curve that rises in temperature with time andstabilizes at a certain temperature as the heat load application isstarted while the supply temperature of the brine adjusted to thespecified temperature is maintained constant.

[0130] In the latter case of heat load change, the first temperaturechange curve L1 shows a curve that drops in temperature with time andstabilizes at the work setup temperature SV(R) as the heat loadapplication is stopped while maintaining the brine supply temperatureconstant.

[0131] Next, it acquires an imaginary second temperature change curve L2of the work W, which is in axial symmetry with the first temperaturechange curve L1, based on the work setup temperature SV(R). Next, atarget temperature change curve L3 is calculated to realize the acquiredsecond temperature change curve L2. Although the target temperaturechange curve L3 is shown on the lower temperature side relative to thesecond temperature change curve L2 in the conceptual diagram of FIG. 10,it may coincide with or become shifted on the higher temperature siderelative to the second temperature change curve L2 depending on theenvironmental temperature or the setup temperature.

[0132] The controller 170 controls the adjusting unit in such a way thatthe brine supply temperature Pt1 changes according to the targettemperature change curve L3 when it detects that the heat load appliedto the work W by the external heat source 31 has been changed. Thisadjusting unit is a general name given to various means required foradjusting the brine supply temperature Pt1 and includes a refrigerator50, an electric heater 61, and a valve 114.

[0133] In case of starting the supply of the heat load by means of acontrol that sets up the brine target temperature predictively, the heatquantity applied to the work W by the external heat source 31 can beapproximately equalized with the heat quantity taken away from the workW by the brine. If the application of the heat load is stopped, the heatquantity dissipated from the work W can be approximately equalized withthe heat quantity applied to the work W by the brine. As a result, evenif a big heat load change occurs, hunting phenomena in the worktemperature are less likely to occur compared to feedback controls suchas the PID control, thus making it possible to control the temperatureof the work W more constantly and improve the stability of the controlfor adjusting the work W to the work setup temperature SV(R).

[0134] Although there is a case when the heat quantity of the heat loadin acquiring the first temperature change curve L1 differs from the heatquantity of the heat load for actually controlling the temperature ofthe work W, the effect of the difference in heat quantity on the firsttemperature change curve L1 is known to be proportional. Therefore, thesecond temperature change curve L2 and the target temperature changecurve L3 can be acquired by compensating the first temperature changecurve L1 in accordance with the difference in heat quantity. It is alsopossible to acquire multiple first temperature change curves L1 fordifferent heat quantity in advance and calculate the first temperaturechange curve L1 by means of interpolation calculation that matches theheat quantity of the heat load that was actually applied based on thosemultiple first temperature change curves L1.

[0135] The operation of the second embodiment will be described belowreferring to FIG. 11 through FIG. 16, showing a flow chart, FIG. 17,FIG. 18A and FIG. 18B.

[0136] The operating mode of the brine supply device 10B is divided intothe sampling mode for acquiring data necessary for controlling the brinesupply temperature predictively and the work temperature control mode,which is the normal operation. It is necessary to execute the samplingmode when the brine supply device 10B is first installed. In thesampling mode, the brine target temperature when the process side heatload is 0%, i.e., SV(S) [0], and the brine target temperature when theprocess side heat load is 100%, i.e., SV(S) [100], are determined. Also,the process of acquiring the first temperature change curve L1 of thework W (see FIG. 10) is executed. Further, the time constant T1 in caseof lowering the brine supply temperature according to the firsttemperature change curve L1 and the time constant T2 in case of raisingthe brine supply temperature are determined as well. The time constantsT1 and T2 can be manually inputted from the digital key pad thatconstitutes the setup unit 72, in addition to automatic acquisition.Moreover, they can be modified as well. The time constants T1 and T2 arestored in a RAM 77. If the process side conditions (heat dissipation,cooling, etc.) do not change, the time constant T1 matches with the timeconstant T2.

[0137] As shown in FIG. 11, the controller 170 makes a judgment whetherthe time constants T1 and T2 are to be manually inputted (S150), whenthe power of the brine supply device 10B is turned on (S100). If themanual input is to be made (S150: YES), the input of the time constantsT1 and T2 is accepted (S151). The inputted time constants T1 and T2 willbe stored in the RAM 77. The controller 170 makes a judgment whether thesampling mode is selected, and a judgment whether the work temperaturecontrol mode is selected (S200, S300). If the sampling mode is selected,the control advances to the step S201, and if the work temperature modeis selected, it advances to the step 301.

Sampling Mode

[0138] In case of the sampling mode (S200: YES), based on the work setuptemperature SV(R) set up by the user, the controller 170 operates afirst pump 42 and a second pump 62 (S202) when the operating switch isturned on (S201: YES). The controller 170 operates the refrigerator 50(S203), turns on the electric heater 61 (S204), and proceeds to the stepS211 of FIG .12. The process heater 32 is kept turned off, and the heatload to the work W is 0%.

[0139] In the primary circuit 11, the brine sent out from the brine tank41 by the first pump 42 is cooled at a heat exchanger 43 by exchangingheat with refrigerant. The circulating brine through pipes 45 (genericname for pipes 45 a through 45 d) will be cooled to a relatively lowtemperature as the refrigerator starts to operate.

[0140] On the other hand, in the secondary circuit 12, the brine addedwith Joule heat by the electric heater 61 sends out by the second pump62 to the load circuit 20 to circulate at a constant flow rate. Thebrine, which circulates through pipes 65 a through 65 d, 65 g and theload circuit 20, gets heated to a relative temperature due to theoperation of the electric heater 61. The control 170 turns the electricheater 61 on and off based on the current brine supply temperature Pt1,the work temperature Pt2 and the work setup temperature SV(R). As thebrine supply temperature Pt1 rises, so does the work temperature Pt2 asshown in FIG. 17.

[0141] The first temperature sensor 81 detects the brine supplytemperature Pt1, the second temperature sensor 82 detects the worktemperature Pt2, the third temperature sensor 83 detects the returntemperature Pt3, and the flow rate sensor 85 detects the actual brinecirculating flow rate F (S211).

[0142] The controller 170 calculates the deviation between the worksetup temperature SV(R) and the work temperature Pt2, i.e.,dt =SV(R)−Pt2(S212), and determines the brine target temperature SV(S) based on aformula SV(S)=Pt1+dt=Pt1+(SV(R)−Pt2)(S213).

[0143] The controller 170 outputs the manipulated variable based on thedetermined brine target temperature SV(S) to the electric heater 61. Theelectric heater 61 is on/off controlled. In order to lower the brinesupply temperature Pt1, the controller 170 opens the valve 114 for acertain period of time. A required amount of brine is sent from theprimary circuit 11 to the secondary circuit 12 through the connectingline 113.

[0144] Next, the controller 170 makes a judgment whether the worktemperature Pt2 has reached the work setup temperature SV(R) (S214).More specifically, it makes a judgment whether the absolute value ofSV(R)−Pt2 is less than the error tolerance β. The tolerance β is, forexample, 0.1 to 0.2° C.

[0145] If it has not reached the work setup temperature (S214: NO), theprocess returns to the step S211, the controller 170 repeats theabovementioned control (S211 through S214: NO).

[0146] If it has reached the work setup temperature (S214: YES), thebrine target temperature SV(S) is determined as the brine targettemperature SV(S) [0] when the process side heat load is 0% (S215), andwill be stored in the RAM 77.

[0147] Next, the controller 170 makes a judgment whether the timeconstants T1 and T2 are recognized (S216). If the time constants T1 andT2 are already inputted manually, it will be judged that the timeconstants T1 and T2 are recognized (S216: YES), and the process advancesto the step S218. On the other hand, if the time constants T1 and T2 arenot inputted manually, it will be judged that the time constants T1 andT2 are not recognized (S216: NO), and an automatic recognition processfor the time constants T1 and T2 (S217) will be performed. The automaticrecognition process of the time constants T1 and T2 (S217) will bedescribed later.

[0148] As shown in FIG. 17, the process heater 32 will be turned on attime t0 after the brine target temperature SV(S) [0] is determined inorder to determine the brine target temperature SV(S) [100] when theprocess side heat load is 100%. The controller 170 detects that the heatload is applied by detecting the ON signal from the power source 33(S218: YES), and proceeds to the step S221 of FIG. 13.

[0149] In reference to FIG. 13, the processes similar to the steps S211through S214 will be performed at steps S221 through S224. If the worktemperature Pt2 is adjusted to the work setup temperature SV(R) (S224:YES), the brine target temperature SV(S) is determined as the brinetarget temperature SV(S) [100] when the process side heat load is 100%(S225), and will be stored in the RAM 77.

[0150] Next, the controller 170 set the difference between the SV(S) [0]and the SV(S) [100] as ΔSV(S) (S226), and stores it in the RAM 77.

[0151] When the process heater 32 is turned off (S227: YES) and theoperation switch is turned off (S228: YES), the sampling mode operationwill be terminated and the process returns to the step S200 of FIG. 11.

Automatic Recognition Process of the Time Constants T1 and T2 (S217))

[0152] As shown in FIG. 14, set the brine target temperature SV(S) [0]determined at the step S215 to the brine target temperature SV(S)(S231), and turn on the process heater 32 (S232) while maintaining thebrine supply temperature Pt1 constant. After turning the heat load fromOff to On condition, sampling of the work temperature Pt2 will beconducted at a predetermined time interval. Acquisition of the firsttemperature change curve L1 as shown in FIG. 10 will be initiated. Thework temperature Pt2 will begin to rise as time goes on.

[0153] When it is judged that the change of the work temperature Pt2becomes less than the specified value, and the work temperature Pt2 hassettled down (S233: YES), the time constant T1 for lowering the brinesupply temperature will be calculated and determined based on theacquired first temperature curve L1 (S234).

[0154] After that, the process heater 32 will be turned off whilemaintaining the brine supply temperature Pt1 constant (S235). Thus, thesampling of the work temperature Pt2 will be continued at a specifiedtime interval even after the process side heat load is switched from theOn state to the Off state to continue to acquire the first temperaturechange curve L1. The work temperature Pt2 lowers with time.

[0155] When it is judged that the work temperature Pt2 has been adjustedto the work setup temperature SV(R) (S236: YES), the time constant T2for raising the brine supply temperature will be calculated anddetermined based on the acquired first temperature curve L1 (S237).

[0156] The acquired first temperature change curve L1 and the dataconcerning the automatically acquired time constants T1 and T2 will bestored in the RAM 77.

Work Temperature Control Mode

[0157] In reference to FIG. 11, while it is in the work temperaturecontrol mode (S300: YES), the controller 170, when the operation switchis turned on (S301: YES), turns on the first pump 42 and the second pump62 (S302), turns on the refrigerator 50 (S303), and turns on theelectric heater 61 (S304) similar to steps S202 through S204.

[0158] While maintaining the process heater 32 in the Off state, thecontroller 170 adjust the work temperature Pt2 to the work setuptemperature SV(R) performing processes similar to the steps S211 throughS214. In other words, the controller 170 repeats the cycle ofdetermining the brine target temperature SV(S) based on the brine supplytemperature Pt1, the work temperature Pt2 and the work setup temperatureSV(R) as well as the turn on/off control of the electric heater 61 andthe turn on/off control of the valve 114 based on the brine targettemperature SV(S) determined in the above until the absolute value ofthe SV(R)−Pt2 becomes less than the error tolerance β in order to adjustthe work temperature Pt2 to the work setup temperature SV(R).

[0159] After it has reached the stable condition, the controller 170constantly monitors whether the heat load to the work W by the externalheat source 31 is changed.

[0160] When the process heater 32 is turned on at time t0 shown in FIG.18B, the controller 170 detects that the heat load application has beeninitiated by detecting the On signal from the power source 33 (S311: YESin FIG. 15).

[0161] When the heat load application to the work W is initiated, theheat storage on the work W starts, so that it becomes necessary to lowerthe brine supply temperature. Hence, the controller 170 calculates thebrine target temperature SV(S) based on the SV(S) [0], the SV(S) [100],and the time constant T1 for lowering the brine temperature (S312). Itis calculated according to the following formula:

SV(S)=SV(R)−ΔSV(S)×{1−e ^((−t/T1))}

[0162] where

[0163] SV(R): work setup temperature

[0164] ΔSV(S): SV(S) [0]−SV(S) [100]

[0165] t: time

[0166] T1: time constant for lowering the brine supply temperature.

[0167] The controller 170 detects the heat quantity actually applied tothe work W based on the output electric power signal from the powersource 33 on the process side. If there is a difference between the heatquantity of the heat load when the first temperature change curve L1 isacquired and the detected heat quantity, the controller 170 willcompensate the first temperature change curve L1 for the heat quantitydifference and will perform the above calculation after the compensationof the SV(S) [100].

[0168] The calculated brine target temperature SV(S) will be atemperature that conforms to the brine target temperature curve L3 torealize the second temperature change curve L2, which is in axialsymmetry with the first temperature change curve L1, as explained in thedescription of the basic operation principle.

[0169] Next, the controller 170 detects the brine supply temperaturePt1, the work temperature Pt2, the brine return temperature Pt3, and theactual circulating flow F of the brine (S313), and determines whetherthe work temperature Pt2 has reached the work setup temperature SV(R)(S314). More specifically, a judgment is made whether the absolute valueof SV(R)−Pt2 is less than the error tolerance β.

[0170] If the work temperature Pt2 is adjusted to the work setuptemperature SV(R) (S314: YES), the brine target temperature SV(S) willnot be compensated and the existing brine target temperature SV(S) willcontinue to be used (S315). The controller 170 repeats the above control(S312 through S315, S319: NO) until the process heater 32 is turned off(S319: YES). The on/off control of the electric heater 61 and the on/offcontrol of the valve 114 will be continued based on the brine targettemperature SV(S).

[0171] If the work temperature Pt2 has not reached the setup temperatureSV(R) (S314: NO), the brine target temperature SV(S) will becompensated. In other words, the controller 170 calculates the deviationbetween the work setup temperature SV(R) and the work temperature Pt2,i.e., dt=SV(R)−Pt2, (S316), sets the SV(S) [100]+dt at the new SV(S)[100](S317), and sets the ΔSV(S)+dt as a new ΔSV(S) (S318).

[0172] The controller 170 repeats the above control process until theprocess heater 32 is turned off (S319: YES) recalculating the brinetarget temperature SV(S) using the new ΔSV(S) (S312 through S314: NO,S316 through S319: NO).

[0173] When the process heater 32 is turned off at time t1 shown in FIG.18B, the controller 170 detects that the turn off signal from the powersource 33 to determine that the application of the heat load is stopped(S319: YES). The process then proceeds to the step S321 shown in FIG.16.

[0174] When the heat load to the work W is stopped, heat dissipationfrom the work W starts, so that it is necessary to raise the brinesupply temperature accordingly. Thus the controller 170 calculates thebrine target temperature SV(S) based on the SV(S) [0], the SV(S) [100],and the time constant T2 for raising the brine temperature (S321). It iscalculated according to the following formula:

SV(S)=(SV(R)−ΔSV(S))+ΔSV(S)×{1−e ^((−t/T2))}

[0175] where

[0176] SV(R): work setup temperature

[0177] ΔSV(S): SV(S) [0]−SV(S) [100]

[0178] t: time

[0179] T2: time constant for raising the brine supply temperature.

[0180] The calculated brine target temperature SV(S) is a temperatureconforming to the target temperature change curve L3 of the brine.

[0181] Next, the controller 170 detects the brine supply temperaturePt1, the work temperature Pt2, the brine return temperature Pt3, and theactual circulating flow F of the brine (S322), and determines whetherthe work temperature Pt2 has reached the work setup temperature SV(R)(S323). More specifically, a judgment is made whether the absolute valueof SV(R)−Pt2 is less than the error tolerance β.

[0182] If the work temperature Pt2 is adjusted to the work setuptemperature SV(R) (S323: YES), the brine target temperature SV(S) willnot be compensated and the existing brine target temperature SV(S) willcontinue to be used (S324). The controller 170 repeats the above control(S321 through S324, S328: NO, S329: NO) as long as the operation iscontinued (S328: NO) until the process heater 32 is turned on (S329:YES). The on/off control of the electric heater 61 and the on/offcontrol of the valve 114 will be continued based on the brine targettemperature SV(S).

[0183] If the work temperature Pt2 has not reached the setup temperatureSV(R) (S323: NO), the brine target temperature SV(S) will becompensated. In other words, the controller 170 calculates the deviationbetween the work setup temperature SV(R) and the work temperature Pt2,i.e., dt=SV(R)−Pt2, (S325), sets the SV(S) [0]+dt at the new SV(S)[0](S326), and sets the ΔSV(S) +dt as a new ΔSV(S) (S327).

[0184] The controller 170 repeats the above control process until theprocess heater 32 is turned on (S329: YES) as long as the operation iscontinuing (S328: NO) recalculating the brine target temperature SV(S)using the new ΔSV(S) (S321 through S323: NO, S325 through S328: NO,S329: NO).

[0185] When the process heater 32 is turned on (S329: YES) while theoperation is continuing (S328: NO), the process advances to the stepS312 of FIG. 15 to execute the above-mentioned control process to beperformed when the heat load application to the work W is initiated.

[0186] When the operation switch is turned off (S328: YES), the worktemperature control mode operation will be completed and the processreturns to the step S200 of FIG. 11.

[0187] According to the brine supply device 10B of the secondembodiment, the temperature rising characteristic of the work W when theprocess heater 32 is turned on from the Off state and the temperaturedropping characteristic of the work W when the process heater is turnedoff from the On state while maintaining the brine supply temperature arestored. Therefore, the brine target temperature SV(S) can be calculatedto match the heat load change without any delay in timing with thechange in the heat load applied by the process heater 32 to the work W,i.e., coinciding with the detection of the start of the heat loadapplication or stop of the heat load application. Thus, since the brinetarget temperature SV(S) is set up predictively before the temperaturechange due to the change of the heat load applied to the work W appearson the work W, the difference between the work temperature Pt2 and thework setup temperature SV(R) is not as large in case of feedbackcontrols such as the PID control. Consequently, even if a large heatload change is imposed, the temperature of the work W can be controlledto a set value with lesser hunting than in feedback controls, and a muchhigher control stability can be achieved in adjusting the work W to thework setup temperature SV(R).

[0188] Furthermore, since a small discrepancy between the worktemperature Pt2 and the work setup temperature SV(R) is fed back tocompensate the brine target temperature SV(S) if the difference betweenthe two temperatures exceeds the error tolerance β, the temperaturecontrol of the work W can be done with a high accuracy.

[0189] Thus, the brine supply control device 10B provides a high speedfollowing capability responding with temperature changes of the work Wto which the applied heat load changes as shown in FIG. 10B, and iscapable of further stabilizing the work temperature Pt2. For example, itwas proven that it can control the temperature of the work W to such ahigh accuracy as ±0.5° C. The heat load change, i.e., the on/offswitching of the process heater 32 is typically provided at every 5minutes. The typical heat quantity applied by the process heater 32 is500W.

Modified Example

[0190] While the work temperature Pt2 is detected by measuring thetemperature of the plate 24, on which the work W is mounted, by means ofthe second temperature sensor 82 in the embodiment described above, thedetection of the current temperature of the work W is not limited tosuch a case. It is possible to make the second temperature sensor 82contact directly with the work W and directly measure the currenttemperature of the work W. Moreover, it is possible to determine thecurrent temperature of the work W by measuring the temperature of thebrine that comes in contact with the work W.

[0191] The invention is not restricted to various embodiments describedabove, and various modifications and changes can be made withoutdeviating from the technological concept of the invention.

What is claimed is:
 1. A temperature control device characterized incomprising: a primary circuit that adjusts the temperature of a firstheating medium to a specified temperature; a secondary circuit thatadjusts the temperature of a second heating medium supplied to a load toa target temperature (SV(S)); a valve that adjusts the flow rate of thefirst heating medium that is mixed with or exchanges heat with thesecond heating medium; a supply temperature detection unit that detectsthe current supply temperature (Pt1) of the second heating medium; a PIDarithmetic unit that calculates the manipulated variable (MV) of saidvalve based on the target temperature (SV(S)) of the second heatingmedium, the current supply temperature (Pt1) of the second heatingmedium, and a predetermined set of PID constants; a compensationarithmetic unit that calculates a compensated manipulated variable (MV′)by compensating the manipulated variable (MV) calculated by said PIDarithmetic unit; and a control unit that controls the operation of saidvalve based on the compensated manipulated variable (MV′), wherein thevariation (ΔMV) of the manipulated variable (MV) is made proportional tothe variation (ΔPV) of the current supply temperature (Pt1) of thesecond heating medium by means of controlling the operation of saidvalve based on the compensated manipulated variable (MV′).
 2. Thetemperature control device of the claim 1 wherein, a compensation factork (0≦k≦1), by which the manipulated variable (MV) is multiplied at thecompensation arithmetic unit, is defined as follows:k=1−(Pt1−PV1)(1−n)/(PV2−PV1) where, PV1: lower limit of the operatingtemperature of the second heating medium; PV2: upper limit of theoperating temperature of the second heating medium; Pt1: current supplytemperature of the second heating medium; and n: a constant for limitingthe manipulated variable when the second heating medium supplytemperature is equal to the upper limit PV2.
 3. The temperature controldevice of the claim 1 further comprising: a setup unit that sets up thetarget temperature (SV(S)) of the second heating medium.
 4. Thetemperature control device of the claim 1 further comprising: a loadtemperature detection unit that detects the current temperature (Pt2) ofthe load; a setup unit that sets up a setup temperature (SV(R)) of theload; and a target temperature arithmetic unit that calculates thetarget temperature (SV(S)) of the second heating medium based on thesetup temperature (SV(R)) of the load, the current temperature (Pt2) ofthe load, and the current supply temperature (Pt1) of the second heatingmedium.
 5. The temperature control device of the claim 4 , wherein saidload temperature detection unit detects the current temperature (Pt2) ofthe load by means of detecting the temperature of the load itself, thetemperature of the second heating medium that is in contact with theload, or the return temperature of the second heating medium that haspassed the load.
 6. The temperature control device of the claim 1 ,wherein said primary circuit adjusts the temperature of the firstheating medium that passes through said valve to a temperature lowerthan the target temperature (SV(S)) of the second heating medium.
 7. Thetemperature control device of the claim 1 , wherein said secondarycircuit further comprises a heating unit that heats the second heatingmedium.
 8. The temperature control device of the claim 1 , wherein saidvalve is a on/off valve that makes the flow rate of the first heatingmedium to zero or maximum, or a flow control valve that continuouslychanges the flow rate of the first heating medium.
 9. A temperaturecontrol device that maintains the temperature of a load, whose heat loadapplied by an external heat source varies, to a setup temperature(SV(R)), comprising: a supply temperature detection unit that detectsthe current supply temperature (Pt1) of a heating medium supplied to theload; a load temperature detection unit that detects the currenttemperature (Pt2) of the load; an adjusting unit that adjusts the supplytemperature (Pt1) of the heating medium; an acquiring unit for acquiringin advance a first temperature change curve (L1) of the load when saidheat load is changed while maintaining the supply temperature (Pt1) ofthe heating medium constant; a first calculating unit for calculating animaginary second temperature change curve (L2) of the load, which is inaxial symmetry with said first temperature change curve (L1), based onthe setup temperature (SV(R)) of the load; a second calculating unit forcalculating a target temperature change curve (L3) of the heating mediumfor realizing said second temperature change curve (L2); and a controlunit for controlling said adjusting unit so that the supply temperature(Pt1) of the heating medium changes according to said target temperaturechange curve (L3) when the heat load applied to the load by saidexternal heat source is changed.
 10. The temperature control deviceaccording to the claim 9 wherein said control unit detects that the heatload applied by said external heat source to the load has been changed.11. The temperature control device according to the claim 9 wherein saidcontrol unit detects heat quantity actually applied to the load by saidexternal heat source.
 12. The temperature control device according tothe claim 11 wherein said first calculating unit compensates the firsttemperature change curve (L1) based on the heat quantity actuallyapplied to the load.
 13. The temperature control device according to theclaim 9 wherein said adjusting unit comprises a cooling unit that coolsthe heating medium; and a valve that mixes a portion of the mediumcooled by said cooling unit to the heating medium supplied to the load.14. The temperature control device according to the claim 9 wherein saidadjusting unit comprises a heating unit that heats the heating medium.15. The temperature control device according to the claim 13 furthercomprising: a buffer tank placed between said valve and the load. 16.The temperature control device according to the claim 15 wherein saidbuffer tank removes temperature uneveness of the heating medium suppliedto the load.
 17. The temperature control device according to the claim 9wherein said load temperature detection unit detects the currenttemperature (Pt2) of the load by means of detecting the temperature ofthe load itself or the temperature of the heating medium that is incontact with the load.